A cylinder-head is mounted to an internal combustion engine block for enclosing one or more cylinders and providing at least a portion of the combustion chamber. Depending on the cylinder configuration of the engine, one, two or more cylinder-heads may be employed. The cylinder-head is sealed to the engine block and often provides porting for feeding fuel and air to the cylinder, while also exhausting the post-combustion exhaust. The porting is often regulated by a valve train, which is often assembled to the cylinder-head. Thus a cylinder-head in combination with a valve train is often referred to as a cylinder-head assembly. The operation of the valve train is driven by at least one camshaft. In overhead camshaft designs, the camshaft is supported for rotation in the cylinder-head assembly.
The valve train often includes poppet valves which are received for reciprocating translation in valve guides in the cylinder-head. During assembly, a valve stem is inserted into a combustion side of the cylinder-head. After installation, a valve plug is typically maintained in the installed position by a fixture or automation. The cylinder-head is typically flipped over, and valve springs, spring caps, and retainer keys are installed to the valve stem. The springs are compressed, permitting the spring cap and retainer keys to translate along the valve stem until the keys engage a notch on the valve stem. The compression is released so that the spring engages the spring cap thereby loading the valve plug into engagement with the cylinder-head. Installation of the valve train was previously performed manually. Subsequently, the installation was automated with the valves installed at a separated cell or station than the valves springs, springs caps and retainer keys.